Sigh...I broke something - PeachParts Mercedes-Benz Forum

bd1308 · #1 11-22-2011, 09:57 PM

Hello. I was attempting to effectively disable the EGR by unplugging and blocking the vacuum ports with golf tees (until I can fashion a blockoff plate)

Good news: My vac leaks are gone.

Bad News: There's something wrong with the bleedoff from the VCV or something. The transmission is flaring like crazy now.

It seems like there's something wrong with how the vacuum is setup on my car.

Does anybody have a good picture of their engine bay?

84 300D Federal

kerry · #2 11-22-2011, 10:12 PM

You've got too much vacuum going to the transmission. It sounds like someone had adjusted the VCV or transmission to adjust for the leaks and now that they're gone, it's flaring. Unplug the line going from the VCV to the transmission and you should get hard shifts.

bd1308 · #3 11-22-2011, 10:16 PM

Okay...Thats exactly what I figured. I pulled over and unplugged the Y going from the bottom of the VCV and going to the transmission. Made a SSSHHHHOOP sound when i unplugged it, so I know it was under vacuum.

No change, still flared, which is why I think that the vac lines arent right.

I did block off EGR, is there a possibility that the EGR lines provided vac bleed between the two "groups" of vacuum lines? In my car there's two Y's and one of the Y's was plugged into the bottom of the transmission. There's a X too, but the X and one of the Y's comes from the brake booster lines, which I would expect is normal.

bd1308 · #4 11-22-2011, 10:17 PM

It almost seems like I should post a picture of my car's vac setup and then people can pick through that....The search function is a little poor. Same experience ive had with other boards

kerry · #5 11-22-2011, 11:32 PM

Are you saying that you removed the vacuum line going from the VCV down to the transmission? If so, I believe your transmission should not be getting any vacuum at all. So if it's still flaring with no vacuum lines connected to it, something else is going on.

bd1308 · #6 11-22-2011, 11:53 PM

That's what I thought too. I'm going to look at it tomorrow. The transmission used to (around a month ago) shift hard, but since i plugged the leaks, its shifting too soft.

Thanks for the help

bd1308 · #7 11-23-2011, 08:20 AM

I decided to try unhooking this seemingly random black tube from the system before taking off and bingo it was the correct one.

Turns out that black line was connected to the the same T as the green dashpot and the line going into the VCV. So the transmission was not only seeing very high vacuum pressure, it also never modulated to zero-ish according to throttle position.

Any hints on searching? I looked around on google and found lots of emissions diagrams, but nothing for the rest of the vacuum system. I figure the green dashpot and the black line should be on either side of the VCV, and the other stuff can connect to the other tee's in the system. There's a slight difference in the two nipples on the power steering line, but I'm not really sure which way things are supposed to hook up.

charmalu · #8 11-23-2011, 12:00 PM

Did you see these links?

Transmission:

Charlie

scottmcphee · #9 11-23-2011, 04:20 PM

Pay attention to any missing flow restrictors that should appear at various places long the vacuum lines. These are color coded discs with double butt ends that insert into the vac line. The color defines the size of the pin hole inside. Without these restricted orifices there is too much available vacuum reservoir for controlled bleed-off to occur. It could take a substantial vacuum leak somewhere to compensate for a missing orifice disc, and when you solve the leak, the need for the restrictor becomes all too apparent.